The invention relates to a device for characterising OSI-material in which the material is subjected to a gas mixture containing oxygen and then volume part of the gas mixture is measured with regard to its oxygen concentration.
Various analytic apparatus and methods for characterising O2-scavengers falling under the term of OSI-materials are known. In gas chromatography for example, a certain quantity of an O2-scavenger is subjected to a gas mixture which contains oxygen. After a certain time in which the O2-scavenger breaks down the oxygen from the gas mixture, a certain quantity of the present gas mixture is lead to a measurement apparatus, in which the gas to be analysed is separated from the gas mixture via a separating column, and is quantified via a detector, e.g. a helium pulsed-discharged-detector.
Furthermore, electrochemical methods, using e.g. O2-sensitive electrodes are known, which detect the oxygen change in a compartment via an electrochemical reaction. There are also pressure measurement methods with which the pressure change in a rigid compartment is detected via a pressure sensor. Thereby, the pressure change is directly proportional to the oxygen change caused by the O2 scavenger. Furthermore, fluorescence measurement technology may be applied, with which the fluorescence quenching of an actively excited, O2-sensitive dye is detected. The fluorescence quenching is indirectly proportional to the oxygen concentration.
At present, no special measurement technology exists for characterising O2-indicators, which likewise represent an OSI-material.
O2-scavengers are substances which absorb and/or adsorb the oxygen. The systems which have established themselves on the market today may be primarily classified according to the O2-scavenger substrate and according to their initialisation mechanism. With the classification by way of the O2-scavenger substrate, one differentiates according to inorganic O2-scavengers, e.g. iron-based or sulphite-based systems, according to low-molecular organic O2 scavengers, e.g. ascorbate-based systems, and according to high-molecular organic O2-scavengers, e.g. polyolefin-based or polyamide-based systems. The O2-scavengers are either UV-initialised or humidity-initialised. This means that the O2-scavenger function is only present after an exposure to UV-light or humidity.
Indicator systems may generally be divided into time-temperature indicator systems (TTI), gas/leakage indicator systems and freshness indicator systems. Time-temperature indicators integrate the time-temperature history of a product and thus provided direct information on its storage conditions. The indicator effect is effected by way of a chemical reaction or by way of counter-diffusion of two dyes. Gas/leakage indicators detect the gas concentration, e.g. O2, CO2 or H2O in the packaging space of a product. They thus provide indirect information on the quality of the product. The indicator effect is caused by a chemical reaction with the respective gas as a reactant. Freshness indicators detect the metabolism products of micro-organisms and thus provide direct information on the quality of the product. The indicator effect is caused by a chemical reaction of the metabolism products. All mentioned indicator systems represent their indicator effect by way of a visible colour change.
OSI-materials, specifically O2-scavengers, O2 indicators or O2-scavenger/O2-indicator systems are applied in the foodstuff industry, pharmaceutics industry, electronics industry, chemical industry, and with other applications. In order to be able to adapt these OSI-materials in their quantity, their effect and other parameters, to the demands of the respect set aims, it is necessary to characterise the respective OSI-material, wherein the basis of the characterisation is the oxygen concentration with regard to a time component.